General information
EP260302a is a fast X-ray transient detected by Einstein Probe/WXT with an automated EP/FXT follow-up that refined the position to arcsecond scales. Multiple facilities report a coincident optical counterpart (showing fading and later rebrightening), a spectroscopic redshift measurement, and a radio counterpart.
Wavelength coverage
- X-ray: EP/WXT detection and EP/FXT follow-up with reported fluxes and spectral indices.
- Optical: Detections and multi-epoch photometry from BOOTES-7, LCO, Gemini-S, and SVOM/VT; late-time upper limits also reported by MASTER.
- Radio: MeerKAT detection at 3.06 GHz (~170 uJy/beam).
Bands with no observations mentioned: gamma-ray, UV, infrared, millimeter/sub-mm.
Lightcurve and spectrum
- X-ray: WXT shows a flare within the first 100 s; FXT light curve declines during its observation. Reported power-law indices: WXT ~1.1 (0.5–4 keV), FXT 1.46(+0.04/-0.04) (0.5–10 keV), with NH including a Galactic-fixed component and an additional fitted component.
- Optical photometry evolution: ~19.1 mag (clear, ~11 min) and ~19.8 mag (w calibrated to R, ~1 hr), fading to r=20.84 and z=20.38 at ~2.46 hr, then r=22.06 at ~7.8 hr. Later measurements show rebrightening to r=21.07 at ~67.4 hr, followed by r=21.30 at ~3.18 d; SVOM/VT reports VT_B=21.4 and VT_R=21.2 at ~58.0 hr.
- Optical spectrum: Continuum detected from 4470–8500 Å; absorption features identified.
Redshift
Gemini-S/GMOS spectroscopy reports absorption features (Fe II and Mg II) consistent with z = 1.535, and additionally infers an upper limit z < 2.67 from the lack of hydrogen absorption.
What’s special vs typical
The optical counterpart shows a reported rebrightening by ~1 mag around ~67 hr after trigger, described as uncommon for FXT and GRB afterglows at that epoch.